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1999 Shadow 750 ACE VT750CD3 Modified
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You are probably going to need Keihin sized main jets of larger size I'm guessing a 132 front and 135 rear just to get it to run at all so you can start the tuning procedure that @Froth indicates.
Follow it!!
142 pilots are going to work OK I think as will the Dynojet needles.

There are a couple of things to consider forward facing intakes such as the "Spike" create an unstable variable "ram air" effect that is impossible to get right for all conditions with carbs and also in rain conditions they will vacuum up a lot of water.
 

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1999 Shadow 750 ACE VT750CD3 Modified
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4,553 Posts
One other thing I’ve always wondered about is if the turbulence of the airflow disrupts the CV piston in the carb throat. The ‘nylons’ example is an extreme one, but if someone had ever put an aluminum honeycomb into the intake pipe, like the kind you get in Mass Airflow sensors to ‘smooth’ the airflow, I’m wondering if that would help… 🤔
The spike air filter maintains the OEM air box and intake runners to the carbs and "just" replaces the filter box, so it is not as bad as sticking pods directly on the carb air horns, which does cause turbulence and fluttering of the slides and fuel stand off. On my bike I increased the length of the slide springs and retempered following dyno proven success of folks on the Hawk GT forum. This gives the slide more seat pressure and avoids flutter, the throttle response remains OK-ish.

Ideally the Intakes would have long runners between the carbs and filters, this can't fit due to everything being stuffed in the limited space of the V of the cylinders.
This also affects the available space for any honeycombs, slats or grilles or other gizmos and with the limited available space they end up stuffed in the air steam restricting the net flow though the carburetor(s). Such stuff has been used successfully with various engines with decent size airboxes/plenums to calm down the air entering the plenum and the engine sees stable unrestricted air from plenum and as long the intake to the plenum is sufficiently sized.

The more you look at it Honda did a pretty good job, within the compromised space with the design of the OEM intake system, given the physical space and noise constrains they have to deal with, it does the job.

Personally I'm a big fan of the "Bean box mod" of the 750 ACE and Spirit, with appropriate rejetting, the only drawbacks are increased intake noise (sounds cool though) and the thing is still in the way of your knee. (-;
 
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